JSFiddle - React, Tailwind, and code Playground

HTML

<h1 id="result">none</h1>
<ol id="fib">
    
</ol>

JavaScript

var ol = document.getElementById("fib");

function fib(n) {
    ol.innerHTML += ("<li>STARTED Fib <b>" + n + "</b></li>\n");
    if (n <= 0) return 0;
    if (n == 1 || n == 2) return 1;
    
    return fib(n - 1) + fib(n - 2);
}

var h1 = document.getElementById("result");
h1.innerHTML = fib(11);